1. Field of the Invention
The invention relates to land vehicles and especially to wheeled land vehicles of the extensible type wherein the wheels are vertically adjustable and the load surface is below the wheel axis, and also to wheeled land vehicles of the extensible type wherein the wheels are vertically adjustable and are power operated. The invention also relates to material or article handling and specifically to self-loading or unloading vehicles having an elevating load body.
2. Description of the Prior Art
Trailers are often used for moving small loads, such as by towing the load behind an automobile. Large loads such as construction machinery of all sizes are also moved on trailers, usually pulled by trucks. Some trailers are designed for use with a specific piece of equipment, but in general, a trailer is not specifically adapted to haul only one item. Thus, because load sizes and weights may vary considerably, a trailer may be subjected to a wide range of loading on its suspension, with the minimum being zero loading above the weight of the trailer itself, and the maximum being the limit set by the physical strength of the trailer structure and the discretion of the operator. At times, therefore, a trailer may be underloaded, with the suspension being overly stiff for the carried load, with the result that the load tends to be harshly bounced. At other times, the trailer may be overloaded, with the result that the suspension exhausts its free movement and cannot absorb an adequate range of shocks. In either case, the load may be damaged by shock, and the trailer itself may suffer damage. Accordingly, it would be desirable to have a utility trailer suspension that is readily adjustable to the load weight so that the load and the trailer are both protected from shock damage.
Conventional trailer design employs an axle across the trailer platform, which determines the height of the trailer bed. Heavy equipment is often difficult to load onto a trailer unless special equipment is available, such as a ramp or winch, since the equipment must be raised to the trailer bed. This problem is most prevalent in the consumer trailer market, in which the trailer may be rented or owned by an individual for family use, since cost and size limitations may result in winches and ramps being unavailable or overly costly. Accordingly, it would be desirable to have an elevating load body on a trailer, wherein the load body could be elevated by equipment that operates in the normal suspension of the trailer, thereby eliminating the cost of extra, single purpose equipment. Correspondingly, it would be desirable to create a suspension system that, through the use of a unitary array of components operating in an integrated manner, could both provide elevator action to the trailer body and tailor the suspension system characteristics to the load weight.
Elevator action has been known for use in trailers and other equipment, such as plows. Elevator systems have employed a bellcrank having the traditional three pivots--one at the end of each of the bellcrank arms and one at the apex. One of the pilots is attached to a frame member, a second member is attached to a wheel axle, and a third is attached to a hydraulic cylinder or the like. In operation, the hydraulic cylinder serves as the prime mover for pivoting the bellcrank on the frame-attached pivot, causing relative vertical movement of the wheel axle and thus, producing elevator action. The bellcrank has been inoperative with regard to suspension system operation, and in some cases the bellcrank has even been locked into position by a fastener to prevent movement when elevator action is not desired. United States patents showing this state of the art are U.S. Pat. Nos. 3,666,129 to Haskins; 3,533,641 to Driskill; 3,240,506 to McMullen; 3,217,911 to McMullen; and 2,712,277 to Rutter.
The present invention provides an integrated elevation and adjustable suspension system that resolves the problems of the prior art as described above.